A bismuth oxychloride / porous organic polymer composite photocatalyst, a preparation method and application thereof

Abstract

The application discloses a preparation method of a bismuth oxychloride / porous organic polymer composite photocatalyst, which comprises the following steps: preparing D-POP by a diazo coupling reaction with 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and m-benzene triol as base materials; and then, through a hydrothermal method, the bismuth oxychloride nanosheet is combined to form a BiOCl / D-POP composite photocatalyst. The bismuth oxychloride is first combined with the porous organic polymer D-POP which has a strong visible light response to construct an organic-inorganic heterojunction system, and the problems of poor visible light response of the bismuth oxychloride and high recombination rate of the photo-generated electron-hole pairs of the porous organic polymer D-POP are effectively solved. The composite photocatalyst has the advantages of high stability and high photocatalytic rate under visible light, and can be applied to degradation of a rhodamine B aqueous solution. The preparation method is simple, the synthetic material and solvent are green and environment-friendly, the application meets the actual production needs, and has a great application prospect.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a bismuth oxychloride / porous organic polymer composite photocatalyst, its preparation method, and its application. Background Technology

[0002] In recent years, various acidic and basic azo dyes have been widely used in industries such as textiles, leather, and papermaking. Typically, dyes cannot be fully utilized during use, resulting in approximately 15% or more of dye wastewater being discharged into the aquatic environment, impacting the ecological environment. Rhodamine B (RhB) is a cationic basic dye. The aromatic ring in the RhB structure makes it difficult to degrade naturally. Furthermore, this dye is carcinogenic; after absorption by the human body, it can affect the liver and nervous system. Therefore, there is an urgent need to find a suitable method to treat RhB dye wastewater.

[0003] Physical methods, including adsorption, membrane filtration, and reverse osmosis, are commonly used to treat dye wastewater. These methods only pretreat the wastewater and cannot truly remove dye molecules. While chemical oxidation can completely oxidize and degrade dyes, the large quantities of chemical oxidants added can easily cause secondary pollution. Biological aerobic and anaerobic oxidation methods are less expensive and less polluting, but their degradation efficiency is lower and their cost is higher. Photocatalysis technology, due to its low cost, high efficiency, and environmental friendliness, has been widely used in the degradation of organic pollutant wastewater, heavy metal ion wastewater, and photocatalytic water splitting for hydrogen production.

[0004] Layered bismuth oxychloride, due to its strong built-in electric field and excellent photogenerated electron transport capability, has been widely studied by researchers. However, its large bandgap results in extremely low solar energy utilization, making it necessary to propose an effective strategy to improve the photocatalytic performance of bismuth oxychloride. A review of numerous publications reveals that researchers typically combine bismuth oxychloride with another inorganic photocatalytic material to form heterojunctions, thereby enhancing its photocatalytic performance. However, reports on combining bismuth oxychloride with organic materials to form organic-inorganic semiconductor heterojunctions are relatively few.

[0005] Porous organic polymers (POPs) possess semiconductor properties. Compared to other inorganic semiconductors, POPs materials exhibit tunable porous structures, high specific surface areas, and broad light absorption ranges. Furthermore, their porous structure facilitates the absorption and diffusion of reactants. However, single-component POPs materials generally suffer from drawbacks such as low photogenerated carrier mobility, rapid recombination of photogenerated electrons and holes, complex preparation processes, and expensive materials, severely limiting their application in photocatalysis. Therefore, combining the distinct advantages of POPs and bismuth oxychloride to form a bismuth oxychloride / porous organic polymer composite photocatalyst is a feasible approach to improve its photocatalytic performance. Summary of the Invention

[0006] This invention provides a bismuth oxychloride / porous organic polymer composite photocatalyst with high photocatalytic activity, multiple active sites, slow photogenerated electron-hole recombination rate, high stability, and high solar energy utilization. It also provides a simple synthesis method and a green and environmentally friendly synthesis material preparation method, and provides an application of the above-mentioned bismuth oxychloride / porous organic polymer composite photocatalyst in visible light degradation of RhB dye wastewater.

[0007] The present invention achieves its objective through the following technical solutions:

[0008] 1. 2,4,6-Tris(4-aminophenyl)-1,3,5-triazine was dissolved in deionized water, and concentrated hydrochloric acid (36%) was added. The mixture was stirred at 0-5℃ to obtain solution A. Sodium carbonate and phloroglucinol were placed in deionized water and stirred at 0-5℃ to obtain solution B. Solution B was added to solution A, and the mixture was stirred at 0-5℃ for 12 h. The solid and liquid were separated. The solid was washed successively with water, anhydrous ethanol, tetrahydrofuran, anhydrous ethanol, and water. It was then vacuum dried at 60℃ for 12 h and ground to obtain brown-black porous organic polymer D-POP powder.

[0009] The molar volume ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to concentrated hydrochloric acid is 1:0.5-1mL, the molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to sodium nitrite is 1:1-3, the molar ratio of sodium carbonate to phloroglucinol is 2-4:1, and the molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to phloroglucinol is 1:1-3.

[0010] 2. Bismuth nitrate pentahydrate, 0.2g polyvinylpyrrolidone, and D-POP were placed in ethylene glycol and stirred until completely dissolved. Then, potassium chloride solution was added, and stirring was continued to form a milky white suspension. The suspension was transferred to a polytetrafluoroethylene cup and heated in a high-pressure reactor at 150-180℃ for 12 hours. Solid-liquid separation was performed, the solid was washed, and dried to obtain the bismuth oxychloride / porous organic polymer composite photocatalyst BiOCl / D-POP.

[0011] The molar ratio of bismuth nitrate pentahydrate to potassium chloride is 1:1, the molar ratio of bismuth nitrate pentahydrate to polyvinylpyrrolidone is 1:1-2, and the mass ratio of bismuth nitrate pentahydrate to D-POP is 1:37-186.

[0012] 3. The bismuth oxychloride / porous organic polymer composite photocatalyst prepared by the above method is applied to the photocatalytic degradation of organic pollutants; specifically, the bismuth oxychloride / porous organic polymer composite photocatalyst is added to an aqueous solution of organic pollutants, stirred in the dark to reach adsorption equilibrium, and then the photocatalytic degradation reaction is carried out under light.

[0013] Compared with existing inventions, the advantages of this invention are:

[0014] (1) This invention uses 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and phloroglucinol as matrix materials and deionized water as solvent to prepare porous organic polymer D-POP in a two-step method. It has the characteristics of simple synthesis process, low synthesis cost, high yield and green environmental protection. The high specific surface area, porous structure and π-π conjugated structure of D-POP give it high photocatalytic activity. At the same time, this invention prepares bismuth oxychloride / porous organic polymer composite photocatalyst by one-step hydrothermal method. The introduction of sheet-like bismuth oxychloride improves the problem of fast photogenerated electron-hole recombination in D-POP and promotes the separation and migration of photogenerated charge carriers. D-POP provides a large number of photocatalytic active sites and the wide light absorption improves the solar light utilization rate of bismuth oxychloride. The two materials complement each other's advantages and disadvantages. The resulting bismuth oxychloride / porous organic polymer composite photocatalyst has the advantages of large surface area, low cost and simple synthesis method, fast separation and migration of photogenerated charge carriers, high photocatalytic activity and good stability. It has good application value and prospects.

[0015] (2) The bismuth oxychloride / porous organic polymer composite photocatalyst of the present invention can remove up to 95% of RhB dye wastewater under visible light, which can meet the needs of practical applications. Attached Figure Description

[0016] Figure 1 The X-ray diffraction patterns of the bismuth oxychloride / porous organic polymer composite photocatalysts (1-DOB, 3-DOB, 5-DOB) in Example 1 of the present invention, the D-POP catalyst in Comparative Example 1, and the BiOCl catalyst in Comparative Example 2 are shown.

[0017] Figure 2 The images are scanning electron microscope images of the bismuth oxychloride / porous organic polymer composite photocatalyst 3-DOB in Example 1 of the present invention, the D-POP catalyst in Comparative Example 1, and the BiOCl catalyst in Comparative Example 2, wherein Figure a is BiOCl, Figure b is D-POP, and Figure c is 3-DOB.

[0018] Figure 3 This is a transmission electron microscope image of the bismuth oxychloride / porous organic polymer composite photocatalyst (3-DOB) in Example 1 of the present invention;

[0019] Figure 4 The X-ray photoelectron spectra of the bismuth oxychloride / porous organic polymer composite photocatalyst (3-DOB) in Example 1 of the present invention and the catalysts of Comparative Examples 1-2 are shown.

[0020] Figure 5 The X-ray photoelectron spectra of the bismuth oxychloride / porous organic polymer composite photocatalyst (3-DOB) in Example 1 of the present invention, the BiOCl catalyst in Comparative Example 1, and the D-POP catalyst in Comparative Example 2 are shown.

[0021] Figure 6 The UV-Vis diffuse reflectance spectra of the bismuth oxychloride / porous organic polymer composite photocatalyst (3-DOB) in Example 1 of the present invention, the BiOCl catalyst in Comparative Example 1, and the D-POP catalyst in Comparative Example 2 are shown.

[0022] Figure 7 The graph shows the removal effect of bismuth oxychloride / porous organic polymer composite photocatalyst (3-DOB) on RhB under different initial pH conditions in Example 4 of this invention. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, the scope of protection of the present invention is not limited to the contents described. Unless otherwise specified, the reagents and methods used in the embodiments are all conventional reagents and conventional methods. Example 1

[0024] (1) Dissolve 0.354g of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine in 100mL of deionized water, add 0.7mL of concentrated hydrochloric acid, stir at 0-5℃ for 20min, add 0.138g of sodium nitrite, and continue stirring for 25min to obtain solution A;

[0025] (2) Dissolve 0.318g sodium carbonate and 0.126g phloroglucinol in 30mL deionized water and stir at 0-5℃ for 20min to obtain solution B;

[0026] (3) Add solution B completely into solution A, stir for 12 h at 0-5℃, filter to obtain brown solid, wash the solid with water, anhydrous ethanol, tetrahydrofuran, anhydrous ethanol and water, dry under vacuum at 60℃ for 12 h, grind to obtain brown-black powder D-POP;

[0027] (4) Place 0.4851g of bismuth nitrate pentahydrate, 0.2g of polyvinylpyrrolidone and 0.0078g of D-POP in 20mL of ethylene glycol and stir for 20min to completely dissolve them to obtain solution C;

[0028] (5) Weigh 1 mmol of potassium chloride and dissolve it in 10 mL of deionized water. Stir for 10 min until it is completely dissolved to obtain solution D;

[0029] (6) Add solution D dropwise to solution C and continue stirring for 30 min to form a milky white suspension. Transfer the suspension to a 50 mL polytetrafluoroethylene cup and heat it in a high-pressure reactor at 160 °C for 12 h. Centrifuge, collect the solid, wash it with water and anhydrous ethanol, and then vacuum dry it at 60 °C for 12 h to obtain the BiOCl / D-POP complex (3-DOB).

[0030] In this embodiment, bismuth oxychloride / porous organic polymer composite photocatalysts with different D-POP addition amounts were also prepared. The method was the same as above, except that in step (4), the amount of D-POP added was 0.0026 g and 0.013 g, respectively, to prepare composite 1-DOB and composite 5-DOB. The X-ray diffraction patterns of composite photocatalysts 1-DOB, 3-DOB, and 5-DOB are shown in the figure. Figure 1 .

[0031] Comparative Example 1: Preparation of BiOCl photocatalyst

[0032] (1) Dissolve 0.4851g of bismuth nitrate pentahydrate and 0.2g of polyvinylpyrrolidone in 20mL of ethylene glycol and stir for 20min to completely dissolve them to obtain solution A;

[0033] (2) Weigh 1 mmol of potassium chloride and dissolve it in 10 mL of deionized water. Stir for 10 min until it is completely dissolved to obtain solution B;

[0034] (3) Solution B was added dropwise to solution A above, and stirring was continued for 30 min to form a milky white suspension. The suspension was transferred to a 50 mL polytetrafluoroethylene cup and heated at 160 °C for 12 h in a high-pressure reactor. After centrifugation, the solid was washed with water and anhydrous ethanol and then vacuum dried at 60 °C for 12 h to obtain the BiOCl photocatalyst, denoted as BiOCl. Its X-ray diffraction pattern is shown in [reference needed]. Figure 1 .

[0035] Comparative Example 2: The D-POP prepared in the examples was used as a photocatalyst, and its X-ray diffraction pattern is shown in the figure. Figure 1 .

[0036] from Figure 1 It can be seen that the diffraction peaks of D-POP have no fixed characteristic peaks, indicating that D-POP has an amorphous structure; all the diffraction peaks of BiOCl are almost matched with its standard PDF card (JCPDS card No. 06−0249); the diffraction peaks of the composite photocatalysts (1-DOB, 3-DOB, 5-DOB) are similar to those of BiOCl, which initially proves the successful preparation of the composite photocatalysts.

[0037] Figure 2These are scanning electron microscope (SEM) images of the bismuth oxychloride / porous organic polymer composite photocatalyst (3-DOB) in Example 1 of this invention, the BiOCl catalyst prepared in Comparative Example 1, and the D-POP catalyst prepared in Comparative Example 2. Figure 2 As can be seen from a, bismuth oxychloride consists of stacked layered nanosheets; D-POP is composed of irregular large particles. Figure 2 b), with irregular pores in the middle; D-POP particles encapsulate BiOCl nanosheets ( Figure 2 c).

[0038] Figure 3 The image shows a transmission electron microscope image of the bismuth oxychloride / porous organic polymer composite photocatalyst (3-DOB) in Example 1 of this invention. The D-POP without lattice stripes encapsulates BiOCl, and the lattice stripes of 0.370 nm and 0.275 nm correspond to the (001) and (010) planes of BiOCl, respectively, further proving the successful synthesis of the composite photocatalyst.

[0039] Figure 4 The infrared spectra of the bismuth oxychloride / porous organic polymer composite photocatalyst (3-DOB) in Example 1, the BiOCl catalyst prepared in Comparative Example 1, and the D-POP catalyst prepared in Comparative Example 2 are shown in the figure. (530 cm⁻¹) -1 Corresponding to the Bi-O bond in BiOCl, 1614 cm -1 and 1400cm -1 The presence of C=N and N=N bonds in the D-POP structure indicates the successful synthesis of the composite material.

[0040] The X-ray photoelectron spectrum of the catalyst is shown below. Figure 5 As can be seen from the figure, the composite photocatalyst of Example 1 is composed of C, O, N, Bi and Cl elements.

[0041] from Figure 6 The UV-Vis diffuse reflectance diagram shows that D-POP has strong light absorption in the 50-800nm ​​range. The introduction of D-POP increases the absorption band edge of the composite material from 335nm to 380nm, enhancing the light absorption capacity of BiOCl and thus improving photocatalytic activity.

[0042] Combination Figures 1-6 The bismuth oxychloride / porous organic polymer composite photocatalyst (3-DOB) in Example 1 of this invention was successfully synthesized.

[0043] Example 2: Application of bismuth oxychloride / porous organic polymer composite photocatalyst in the degradation of RhB dye wastewater

[0044] Weigh 10 mg each of the bismuth oxychloride / porous organic polymer composite photocatalysts (1-DOB, 3-DOB, 5-DOB) prepared in Example 1, the BiOCl catalyst prepared in Comparative Example 1, and the D-POP catalyst prepared in Comparative Example 2, and add them to an RhB solution with an initial concentration of 20 mg / L (solution volume 50 mL). Stir at 300 r / min for 30 min in a dark room to reach adsorption equilibrium. Irradiate with a 300 W xenon lamp (equipped with a 420 nm cutoff filter) for 60 min, and take 3 mL of solution every 10 min to measure the absorbance at 540 nm to calculate the degradation rate.

[0045] See results Figure 7 As shown in the figure, under visible light, the removal rates of RhB by 1-DOB, 3-DOB, and 5-DOB within 30 min were 87.24%, 94.33%, and 87.09%, respectively. The removal rates of RhB by Comparative Example 1 BiOCl and Comparative Example 2 D-POP were 65.75% and 87.24%, respectively. This indicates that the combination of the two monomer materials can significantly improve the photocatalytic activity, with 3-DOB showing the best photocatalytic degradation effect on RhB.

[0046] In summary, the bismuth oxychloride / porous organic polymer composite photocatalyst prepared by this invention has the advantages of high stability and high photocatalytic rate under visible light, and can be applied to the degradation of Rhodamine B aqueous solution, showing great application value and prospects.

Claims

1. A method for preparing a bismuth oxychloride / porous organic polymer composite photocatalyst, characterized in that, The steps are as follows: (1) Dissolve 2,4,6-tris(4-aminophenyl)-1,3,5-triazine in deionized water, add concentrated hydrochloric acid and stir at 0-5℃, add sodium nitrite and stir to mix well to obtain solution A; place sodium carbonate and phloroglucinol in deionized water and stir at 0-5℃ to obtain solution B; add solution B to solution A, continue stirring at 0-5℃ for 12h, then separate the solid and liquid, wash the solid, dry and grind to obtain porous organic polymer D-POP; (2) Bismuth nitrate pentahydrate, 0.2g polyvinylpyrrolidone, and porous organic polymer D-POP were placed in ethylene glycol and stirred until completely dissolved; then potassium chloride solution was added and stirring was continued to form a milky white suspension. The suspension was heated at 150-180℃ for 12h, and the solid and liquid were separated. The solid was washed and dried to obtain bismuth oxychloride / porous organic polymer composite photocatalyst. The molar ratio of bismuth nitrate pentahydrate to potassium chloride is 1:1, the molar ratio of bismuth nitrate pentahydrate to polyvinylpyrrolidone is 1:1-2, and the mass ratio of bismuth nitrate pentahydrate to porous organic polymer D-POP is 1:37-186.

2. The method for preparing the bismuth oxychloride / porous organic polymer composite photocatalyst according to claim 1, characterized in that: The molar volume ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to concentrated hydrochloric acid is 1:0.5-1 mL, the molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to sodium nitrite is 1:1-3, the molar ratio of sodium carbonate to phloroglucinol is 2-4:1, and the molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to phloroglucinol is 1:1-3.

3. The bismuth oxychloride / porous organic polymer composite photocatalyst prepared by the method according to any one of claims 1-2.

4. The application of the bismuth oxychloride / porous organic polymer composite photocatalyst according to claim 3 in the photocatalytic degradation of organic pollutants.

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